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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let num = +prompt('请输入年份: ');
        (num % 4 === 0 && num % 100 !== 0) || (num % 400 === 0) ? alert(`${num}年是闰年`) : alert(`${num}年不是闰年`);
    </script>
</body>
</html>